The present invention relates to dual flush systems used in gravity flush toilets and pertains particularly to an improved trap refill apparatus.
A conventional toilet consists of a bowl, normally containing a volume of water into which is deposited human waste products. The waste products are flushed from the bowl by means of water from a tank or reservoir by means of a flushing apparatus. The flushing apparatus comprises a flapper valve that is raised from its seat to release a predetermined amount of water from the reservoir.
Until recent years the conventional toilet used from 5-8 gallons of water per flush. Water shortages throughout the major portions of the United States has forced major improvements in the toilet, such that as little as 1.6 gallons of water is utilized for a standard flush for solid waste removal.
Even further improvements have led to a dual flushing system, wherein a short flush is utilized to flush liquid wastes, and a long flush is utilized to flush solid wastes. The water is dispensed to the toilet bowl by way of a flush valve and seat, such as a flapper which allows the user to flush most of the tank water for a long flush, or just a portion of the tank water on the short flush. Once the toilet has been flushed, the tank is refilled automatically by a refill valve assembly connected to a water supply.
The refill assembly comprises a float operated valve which functions to open the valve and allow the entry of water when the water level drops below a certain level. The refill mechanism includes means for directing approximately 20-30% of the water into an overflow tube which goes to refill the bowl and the remainder of the water into the tank to refill it. The water is divided so that as soon as the tank has been refilled to the shut-off position, the bowl has been similarly filled so that the trap is sealed.
The drawback of the dual flush systems is that they do not account for the fact that successive short flushes typically will result in a bowl having less and less water, eventually not sealing the p-trap adequately. This frequently results in poor flush performance. It also results in wasting water by requiring double flushing to completely remove bowl contents when the trap is not full at the start of the flush cycle.
Some dual flush systems have overcome this by requiring the fill valve to have a higher than standard refill rate during refill. However, this results in wasted water. When a refill occurs after a long flush, the bowl and trap will be filled before the tank is filled and the water will continue to flow down the drain. The refill valve delivers significantly more bowl refill water on the long flush cycle compared to the short flush cycle. If the trap is adequately filled on the short flush cycle, then the additional bowl refill water will overfill the trap and spill over the weir into the drain on the long flush.
Accordingly, it is desirable that a refill apparatus be available which compensates for both long flushes and short flushes of a toilet.